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General Rules
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2017 Pure Thunder Stock Class Rules

 

All drivers are required to have their own Raceivers for one-way communication with race director official.
Top 5 feature finishers will be required to go to tech area after the race.

 

General

1.

Inspections may occur anytime at the discretion of a race official.

2.

All cars must be strictly stock for make and model of car from front bumper to rear bumper. Minimum wheelbase of 107".

 

Weight

1.

3200lbs with driver.

2.

Ballast allowed but must be attached with two ½" bolts. Ballast not allowed in driver's compartment. Ballast must be painted white with car number and must meet safety rules contained herein.

 

Frame and Roll Cage

1.

Complete bumper-to-bumper OES stock frame for make and model of car. 2"x 3" framing may be used from stock rear shock mount (rear kick up) to rear bumper. "2 x 3" framing MUST appear in stock location. Cars with actual stock rear subs, 2"x 3" bar bracing may be used but still must retain stock appearance.

2.

No Unibody cars. Unibody cars that have been welded to create full frame car not permitted. No Camaros.

3.

107" minimum wheel base.

4.

Rust spots may be repaired.

5.

Any repairs to front stub must retain exact OEM measurements for make and model of car. These repairs are subject to track official approval.

6.

No switching or shifting of any body part or frame.

7.

Roll cage must be composed of a minimum 1 ½" OD .090 thickness round steel tubing.

8.

A four-post roll cage must be installed with minimum 3 door bars on driver's door. Driver's door must have 1/8" steel plate welded.

9.

Minimum 2 bars for passenger side door.

10.

Bars may be added from firewall forward to protect frame and radiator.

11.

Main roll cage can be braced rearward to the kick up of the rear frame.

12.

Drive shaft hoop is mandatory and must be installed 6-8" behind transmission tail shaft. No chains allowed.

 

Body

1.

Stock appearing OEM steel body for make and model of car. Sheet metal skins allowed for fenders, doors, hood, and trunk ONLY and MUST have original OES body lines. Sheet metal skins MUST be same thickness or as close thickness as stock OES steel bodies. Stock steel OEM roof and A-pillars mandatory. No aluminum body pieces allowed. Body must match make and model of car in OEM location.

2.

Stock steel unaltered floor pan.  Penalty may be given if floor is altered

3.

Stock front firewall in stock location. A weight penalty of at least 50lbs will be added for altered fire walls. No exceptions. Roof raking NOT permitted. A weight penalty at the discretion of the tech official may be added if raking of roof is found.

4.

Complete firewall must seal trunk from driver's compartment. 16 gauge sheet metal minimum.

5.

The only allowable modifications to the floor pan or firewall is to repair rust holes. All holes within driver's compartment must be covered with 16 gauge sheet metal.

6.

All inner body panels must be unaltered except doors for roll cage bars.

7.

Hood and trunk must be securely fastened with hood pins or similar.

8.

All doors and body panels must be securely fastened. If stock OEM body, body panels must be welded together.

9.

A fuel cell is mandatory. No stock gas tanks allowed. Fuel cell must be mounted in trunk area between frame rails. Fuel cell must be above center line of rear end differential housing or 12" above ground, whichever is highest. For more specific detail, see Fuel Cell Installation section.

10.

Trunk floor may be cut to accommodate fuel cell. Minimum of two, 12 gauge 1 ½ inch safety straps.

11.

3" spoiler optional. Clear lexan material ONLY. 3 braces mandatory. No side fins at ends of spoiler.

12.

Stock looking plastic front nose pieces allowed. Stock appearing rear bumper covers allowed. Stock style rear and front bumpers mandatory.

13.

Stock style bumper will be securely fastened in place in stock location welded to frame rails. No front or rear bumper shocks allowed.

14.

Front fender wells may be removed.

 

Windshield and Glass

1.

All glass, headlights, tail lights must be removed prior to arrival at the track.

2.

No broken glass shall be in the car. Car must be swept clean.

3.

4 bars minimum in front of driver in window. Bars must be 3/8" minimum with wire mesh fastened.

 

Suspension

1.

OES stock suspension only for make and model of car.

2.

Lower A-arms must be OEM stock for make and model. No aftermarket ball joints. Front upper A-arms may be non-adjustable tubular steel in stock location. No welding or altering of upper A-arms allowed.

3.

Rear suspension arms must be OEM stock for make and model. No aftermarket rear suspension arms permitted.

4.

Stock steering box. Stock pitman arm. Stock center link. Stock tie rod ends. Heim joint style tie rod ends/steering linkage not permitted.

5.

No coil over, overload, cargo ratchet or air assisted shocks permitted.

6.

No racing shocks permitted. Steel shocks only. Shocks must maintain stock OEM for front and rear for make and model and in stock location.

7.

Racing springs allowed. Must maintain stock OEM frame and body heights for make and model of car.

8.

Metric cars may reinforce OEM upper A-frames only.

9.

No lift bars or recovery shocks or spring recoils. Stock shocks only.

10.

No screw jacks.

11.

Steering quickener permitted.

 

Brakes

1.

No altering of stock brakes allowed. Steel brake calipers only.

2.

Cars must have functioning brake on each wheel.

3.

Rear disc brakes allowed. Brake assemblies must be in stock location on all 4 wheels.

4.

Brake pedal must remain in stock location.

5.

No brake bias or proportional valve permitted.

6.

After market pedals allowed

7.

Steel hubs only

8.

Stock style steel rotors only. No aftermarket rotors allowed. No scalloped rotors. No drilled rotors.

 

Fuel Cell Installation

1.

Fuel cell mandatory. 22 gallon maximum capacity. OEM gas tank must be removed.

2.

Bracing in trunk permitted

3.

Trunk floor plan may be cut out to accommodate fuel cell.

4.

Fuel cell must be mounted in trunk area between frame rails with at least 1 ½" clearance on all four sides. Minimum of two, 12 gauge 1 ½ inch wide safety straps mandatory.

5.

No electrical fuel pumps.

6.

Fuel line from trunk to engine compartment must be steel or steel braided. No copper or rubber tubing allowed. Any fuel line that runs through driver's compartment must be enclosed in rigid tubing from inside trunk area to inside engine compartment and must be sealed on both ends. Fuel line system must be approved by race official.

7.

Fuel cell will be minimum of 12" above the ground or above center line of rear differential housing, whichever is highest.

 

Engine

1.

Engine block will be stock OEM small block passenger car for make and model of car.

2.

No 400 blocks.

3.

350ci Chevy/GM, 350ci Ford, and 360ci Chrysler allowed. No aftermarket blocks

4.

Blocks numbers must be legible upon inspection.

5.

Engine must remain stock (see below specifics)

6.

All engines must be stock stroke. 5.7in rods mandatory on Chevy engines.

7.

Engine studs allowed.

8.

Solid or hydraulic cams, no roller cams allowed.

9.

Engine will be mounted in stock OEM position. No alterations of front sub or cross member.

10.

Stock rubber motor mounts. 1 chain will be allowed. In lieu of rubber mounts, solid steel nonadjustable engine mounts may be used.

11.

No engine swapping between make and model of car (no Chevy engines in Ford cars etc.)

12.

Dome pistons not allowed. Flat top pistons allowed.

 

Cylinder Heads

1.

Steel stock heads only.

2.

No aftermarket or bowtie heads allowed.

3.

No angle plug, or any type of factory performance heads allowed.

4.

No Ford SVO heads.

5.

No aluminum heads allowed.

6.

No port work allowed.

7.

Aluminum valve covers with raised crank case breathers/filters permitted.

 

Intake Manifold and Carburetor

1.

One Holley 2 bbl 4412 500cfm with stock 1.378 max venturi bore ONLY.

2.

Manifold must be cast iron and unaltered.

3.

Intake Manifold must be strictly stock for make and model of car. No alterations, porting, or polishing.

4.

No high-rise truck or marine type intake manifolds.

5.

Carburetor may be pulled for intake inspection per race official's discretion.

6.

No fuel injection allowed.

7.

Aftermarket air filter housing and filter allowed.

 

Exhaust

1.

Cast iron exhaust manifolds or headers allowed. No cross over or 180 headers

2.

No center dump exhaust systems.

3.

No marine/boat manifolds.

4.

Exhaust must run underneath car and past driver's seat as to dispel exhaust fumes away from driver.

 

Fuel System

1.

No electric fuel pumps allowed.

2.

Stock manual fuel pump mounted in stock location on engine.

3.

Fuel shut-off valve highly recommended.

4.

No E85 fuel allowed. Maximum gas octane of 110 is permitted.

 

Electrical / Battery

1.

No dual point distributors.

2.

Stock coil in stock location. Stock HEI distributor only.

3.

Battery must be securely mounted inside plastic battery safety box.

4.

Battery box will be securely mounted to frame or roll cage bars behind driver's seat.

5.

Plastic safety box will be securely mounted to battery box.

6.

Battery lines running from battery through front firewall must be mounted in flexible tubing (i.e. garden hose etc.) and sealed at both ends.

7.

Ground wire will be directly attached to frame or roll bar.

8.

A battery disconnect switch/kill switch with clearly marked on/off label is required within reach for safety officials.

 

Cooling System

1.

Stock radiator in stock location.

2.

Aluminum or plastic radiator allowed in stock location.

3.

Aluminum water pump allowed.

 

Transmission

1.

Stock OEM manual or automatic allowed.

2.

OEM stock turbo 350 or 400 automatic with 3 forward gears and 1 reverse gear allowed. Stock torque converter only.

3.

Stock OEM manual transmissions allowed with stock single disc clutch inside an explosion-proof steel bellhousing. No aluminum transmissions.

4.

Aftermarket clutch pedal assembly permitted.

5.

No aftermarket made-for-racing transmissions allowed. (i.e. Bert, Brinn, Falcon)

6.

No powerglides.

7.

Transmission must function at engine idle.

8.

Stock rear transmission mounts only. Stock transmission mount cross member bolted or welded to frame.

 

Rear end differential

1.

Steel Ford 9 inch floater rear end allowed.

2. Stock steel mounts must be in stock location for year and make of car.
3. Must remain stock.

4.

Posi-traction limited slip, locked or welded, spider gears allowed.

 

Wheels

1.

Reinforced racing type steel wheels mandatory.

2.

Bead locks to be used only for right side.

3.

1" lug nuts mandatory on all wheels.

4.

Maximum wheel width is 8".

 

Tires

1.

Tires must be 60 or 70 Series DOT approved.

2.

15" DOT street tire allowed.

3.

Grooving, siping, and/or soaking is not permitted.

4.

Absolutely no racing tires disguised as DOT street tires.

 

Safety

1.

See General Safety Rules page for track specific safety rules.

 

Plymouth Speedway reserves the right to change, delete or add to rules throughout the racing season.
The management reserves the right of interpretation of all rules and the right to inspect and reject
any car and/or driver, crew member, etc. during the racing program.

 

For any questions on the Plymouth Speedway rules, please call Tech Director Mike Zielinski 1-(574) 532-7969

 
 
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Visa, MasterCard, and Discover are accepted at the front gate or the pit gate
and may be used to purchase tires and fuel.

 
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